1. Field of the Invention
The present invention relates to an improvement to a method for making smart cards, of the type having a card body and an electronic module, and cards obtained by implementing the method.
2. Description of the Related Art
Of the existing methods, a method is known of furnishing a card body with a cavity, an electronic module having principally contact pads and a semiconductor chip containing an integrated circuit, and of securing the electronic module in the cavity with gluing means such as a cyanoacrylate glue. In general, the gluing operation is divided into a prior operation in which the module is inserted into the cavity, and a pressing operation of a predetermined length.
However, practical implementation of such a method, usually called "encartage" in French, on an automated industrial scale, which requires separate sequenced operations carried out at different stations, and transferring cards from one station to the next at high speed, on the order of several thousand cards an hour, leads to several problems affecting the quality of the finished product.
In particular, the inventor has found that the cards obtained by gluing using the operations listed above often have major drawbacks.
The principal drawback is incorrect centering of the module in the cavity. Despite correctly centered insertion of the module in the cavity, the inventor found that after gluing some modules were off-center, i.e. had shifted from their initial insertion position. Typically, incorrect centering was slight rotation, or translation, or both at the same time inside the cavity, or in extreme cases outside the cavity with the contact pads having one edge overlapping the surface of the card body.
The inventor found that the incorrect centering resulted in particular from forces produced on the card while it was being moved from one station to another, particularly sudden acceleration or deceleration forces brought about by the card leaving the insertion station and stopping at the pressing station, respectively.
Incorrect centering can also result from residual constraints present in the module which tend to produce a slight inward curvature. In this case, there is a risk of the module popping out of the cavity with each acceleration or deceleration referred to above.
Defects relating to poor adhesion of the module to the card body have also been found. In these situations, the card cannot meet the mechanical strength criteria imposed by current standards (ISO and AFNOR) for bending, twisting, and separating forces.